1994 Diesel Suburban Build

[aardvarcus]

Back in the saddle again!

In an interesting turn of events, Toyota has decided my 2005 Tacoma needs a new frame. With the growing list of maintenance and upgrade items needed on the Suburban, I am temporarily driving my tow vehicle (2001 2500HD 4x4 8.1L/Allison) which gets worse highway fuel economy (14MPGish highway) which in turn has turned up the heat on getting the Suburban completely fixed. Thus I have started and will continue working on it for the next few weeks as my priority project.

So far, I have replaced the failing alternator cs130 with a new unit intended for a Duramax, mainly to pick up more amps at idle to support the electric fans and other mods. Perhaps there is also a slight efficiency gain with this newer style unit, probably not measurable either way. I had to fabricate a new bracket, fairly simple aluminum bar with two bends. The main lower bracket lines up correctly. I now have to rewire the plug, as the newer alternator takes a different plug than the old one. Anyway some pictures are attached.

With a little luck, I hope to have a huge list of things finished over this weekend. My NV4500 main shaft spanner socket just came in the weekend, so hopefully on that list is a NV4500 gear swap and a transmission swap.

[roosterk0031]

My bosses 2006 had it's frame replaced 1 or 2 years ago. 2wd access cab. He bought a $5,000 Tacoma late 90's I think for his son a few years ago, son took it to Toyota dealer for something else a while later, they kept it and gave him $12,000.

[Taylor95]

Are you expecting a substantial increase from the transmission work?

24 mpg is quite impressive on one of those old huge suburbans.

[aardvarcus]

Taylor95,

I don’t expect a huge increase from just the gearing. Currently the truck is way over geared as there is more than enough torque to climb hills in overdrive without shifting, even steep hills at low speeds. Doing the overdrive swap will improve this, down to 1635 RPM @ 55. Of this 11.4% cruising RPM gain, I hope to pick up 3-4% mpg highway gain, or 1 MPG. Hopefully I will be able to test and know for sure soon.

Following that work, future plans for the vehicle include substantial aero mods and differential gear swaps (4.10 to 3.42) and my eventual goal is to be over 30MPG with this vehicle consistently.

[Taylor95]

It would probably be cheaper to just get bigger tires, wouldn't it? Well if you never plan on going off roading, you probably would be more efficient with smaller tires and a higher gear ratio.

Is it a turbo diesel? My dad has a huge truck with a turbo diesel. When I'm driving it in the summer it averages about 24 mpg surprisingly. I'm sure you've considered this before but I think having that could really help push you over 30 mpg.

[aardvarcus]

Taylor95,

I have experimented with tire sizes and tread patterns many times on several 4x4 vehicles, and I have found the most important items for me to be: tread pattern, tread width, and tire diameter in that order. I had nominal 34” tires (255/85R16 Cooper Discoverers) on the vehicle until this August when I put nominal 32” tires (235/85R16 Michelin Defenders) on it, the defenders get better MPG despite the tire gearing loss. I am not aware of any tires with similar highly siped tread and narrow width in a larger diameter than these. I hate running aggressive blocky off-road tires on the highway for a daily driver, they do not perform well. These Michelin tires work well off-road, as long as you do not get into mud where they do not shine. I will probably end up maintaining two sets of tires to be able to swap back and forth for dedicated off-road trips, as I have done on my Tacoma. I do use my vehicles off-road on a regular basis. The Suburban is eventually going to be an expedition-style exploring/camping rig, but first I must get it reliable, functional, and economical to drive.

It is not currently a turbo, I removed the turbo when I put in the newer engine. Against popular opinion, my read of the BSCF and torque curve maps for 6.5L indirect injection diesels leads me to believe the naturally aspirated engine better fits my use case. The 6.5L is not the most efficient diesel engine, just about any direct injection diesel is more efficient, however I chose this engine for other reasons which are documented in the first few posts in this thread. If this project died and I started over, I would probably make different choices today.

[aardvarcus]

Made decent progress over the weekend. Got the late NV4500 disassembled far enough to get the new 5th gear installed. The even with the correct spanner socket, removing the rear dampener was defiantly the biggest problem and the hardest part of the job. Got the new gear on and the transmission reassembled. I disconnected the wiring, pulled the driveshaft, carpet, seats, etcetera to be able to pull the transmission. I removed the transfer case, transmission, and clutch. Had to change the pilot bushing out. I converted the clutch actuator from external to internal, reusing the existing master cylinder but replacing the line set to the new style. I installed the new clutch and transmission and got the transfer case back on. Got the clutch bled. Attached are some photos.

I did some other odds and ends stuff to the vehicle along the way. Spent forever trying to find o-rings and copper washers for the oil filter adapter locally, why does nobody stock anything locally anymore? The cold garage was a damper to my productivity, but I got most of what I wanted done this weekend. I hope between evenings this week and next weekend to finish the outstanding items and to begin daily driving the vehicle again starting next Monday.

[slowmover]

Local stockage? Competition is a sin. And failure to control Deplorables even worse. ONLINE ORDER ONLY!! fits the bill.

An impressive bunch of work!!

[aardvarcus]

Slowmover,
Thanks for the encouragement.

Everyone,
Well my weekend just to work on the Suburban turned into barely having any time to spend on it. Got to help some friends and family with a few projects they would have struggled to do alone. I am still driving my tow pig this week.

Was able to get lots of odds and ends things finished up in the time I did have and took it for a test drive. The transmission shifts fine, but the clutch was not releasing all the way, like you had it slightly pressed in constantly. Long story short, I didn’t realize they changed the shape of the pressure plate fingers for the clutches during the transition from the pre 95 and post 96 bellhousing/clutch styles so I reused the old style pressure plate and the new style concentric slave cylinder is too far forward, pushing it constantly. Thus the clutch would slip under high torque, so I have the correct pressure plate on order. Luckily I have some time off around the holidays so by the new year I will have that changed out and hopefully some more progress.

[aardvarcus]

Made some progress over my holiday break. Removed the transmission and installed the new clutch and pressure plate. Bled the clutch and no more clutch issues. Put some constrained layer dampening sound deadening material on the front floorboards. Rigged up a manual control arm for the HVAC blend door. Replaced the sloppy steering gear with a new PSC unit and bled that system. Swapped the fluids in the differentials over to Amsoil Synthetic gear lube. Retrofitted in an electromotor cruise control system, had to build a new throttle bracket to hold both accelerator pedal and cruise cables. I filled up with diesel on my way to work today, so I will top off tomorrow and have my first MPG reading with the new .64 Overdrive NV4500.